An Edmonton-based Imam is in a Saudi Arabian jail after being beaten and “manhandled” by religious police, according to witness reports. On Sunday morning, Usama Al-Atar, 33, was leading a group of 10 pilgrims in prayer outside the Mosque of the Prophet in Medina when “[Saudi] religious police began to hassle him, and intimidate him into stopping,” according to a release by the U.K.-based Islamic Human Rights Association (IHRA).

Mr. Al-Atar attempted to leave, but he was set upon by guards, labelled a thief, violently restrained and brought into custody.

“It’s very clear that without having committed any crime, [Mr. Al-Atar] has been arrested by the Saudi authorities,” said Mahmood Mavani, president of the Islamic Shia Association of Edmonton, where Mr. Al-Atar is a resident lecturer. On Sunday, Edmonton’s Shia Muslims gathered at the Association’s main congregation hall to pray for Mr. Al-Atar’s release.

Mr. Al-Atar is a Shiite, a sect of Islam that is often subject to persecution in Saudi Arabia. “Mr. Al-Atar is a Canadian citizen and at this juncture we need Foreign Affairs to find out the facts and make sure he is safe,” said Mr. Mavani.

The Department of Foreign Affairs would only say they were “aware of the arrest a Canadian citizen in Medina.” “The Canadian Embassy in Riyadh has been notified and stands ready to provide consular assistance as required,” read a Sunday afternoon email by Department of Foreign Affairs spokesperson Aliya Mawani.

Mr. Al-Atar left Canada on Monday to travel to Saudi Arabia for the hajj, a pilgrimage to Mecca performed annually by more than two million Muslims each year. Mr. Al-Atar was reportedly approached by Saudi religious police while offering prayers at a graveyard — a Shia practice that is frowned upon by Saudi Arabia’s ruling class, who practice a puritanical form of Sunni Islam.

Mr. Al-Atar’s group closed their prayer books and tried to leave the area, but the imam was set upon by guards after the police called out that Mr. Al-Atar was a thief, reported Ahlulbayt TV, a U.K.-based Shia Islamic channel.

The religious police then “manhandled him badly,” eyewitness Mohammed Hayward told IHRA. “They forced him to sit under an air conditioning unit, and squashed him until he was blue in the face.” Mr. Al-Atar’s arrest was witnessed by more than 200 Canadian, American and British pilgrims, the U.K. channel reported.

On Sunday, 60 pilgrims held silent vigil outside the Central Medina jail where Mr. Al-Atar was being held, reported the IHRA. Mr. Al-Atar is scheduled for a court appearance on Monday morning, where he will face accusations that he broke the arm of one of the police — although witnesses say that the Edmonton imam stayed passive throughout the scuffle.

Throughout Sunday, social networks in Canada and the U.K. abounded with appeals to free the imprisoned Canadian. Ahlulbayt TV held an emergency live show on Sunday evening to protest Mr. Al-Atar’s arrest.

The Canadian Council on American-Islamic Relations on Sunday condemned Mr. Al-Atar’s arrest. “Irrespective of any allegations against Imam Al-Attar it is unconscionable that he should be physically assaulted — whether during the Hajj pilgrimage or at any other time,” wrote council executive director Ihsaan Gardee in a prepared release. “If there is no basis for holding Mr. Al-Atar, then he should be immediately released,” he added.

A cancer and diabetes researcher, Mr. Al-Atar is currently a post-doctoral fellow in the chemistry department at the University of Alberta. He has been a prominent voice for inter-faith relations and for stamping out violent extremism within the Islamic community. “Although [terroristic] acts may be carried out by Muslims, these are not the teachings of Islam,” he told Postmedia in 2005.

As recently as March, Mr. Al-Atar publicly denounced the Saudi Arabian leadership. “The atrocities committed today against innocents in several countries such as Bahrain and Saudi Arabia among others, are crimes one cannot stand silent about,” said Mr. Al-Atar in a March speech delivered in Edmonton following violence crackdowns against Arab Spring protesters in the Middle East.

Campaigners for his release fear the severity of the charges against him.

“With Saudis, you never know how extreme they can go,” Montreal-based campaigner Musarrat Pyarali wrote in a letter to the Post.